The subject invention may be utilized with various tufting systems, however, it has particular utility in the "Spanel tufting system" in which yarn strands or bit-lengths of yarn are pneumatically transported to a tufting station where they are implanted in a backing layer by bit-applying elements, such as double needles.
The Spanel tufting system is described in other Spanel patents, including U.S. Pat. No. 3,554,147, which issued to Abram N. Spanel and George J. Brennan on Jan. 12, 1971 and U.S. Pat. No. Re. 27,165 which issued Aug. 10, 1971 to Abram N. Spanel and Lloyd E. Barton.
The aforementioned U.S. Pat. No. Re. 27,165 discloses a pneumatic yarn transport system in which yarn strands and/or discrete bits of yarn are transported pneumatically to a tufting station where they are applied by tufting elements to a backing. Multicolor selection of the yarn bits is enabled by a shifting magazine arrangement which provides yarn of various colors to each of the guide tubes through which yarn is transported to the tufting elements. When the yarn strand or bit reaches the tufting station and threads the dual needles as seen in FIGS. 22A-22D of U.S. Pat. No. Re. 27,165, the yarn impacts against a stop member 23A which maintains it in a desired position relative to the needles preparatory to tufting.
It will be appreciated that in Spanel U.S. Pat. No. Re. 27,165, emphasis was placed on suction, or negative pressure as a means for providing pneumatic yarn transport. A bit-length of yarn was secured in the loading position within the confines of the suction manifold 21, tube passageway 12 and the stop means 23. In later versions of the "Spanel tufting system" as disclosed in co-pending Spanel Application Ser. No. 419,417, a pneumatic yarn transport means employing positive pressure is described. In this application, the yarn bit stop is eliminated and in its place, clamping means are disclosed for holding a yarn bit-length in place in the loading position prior to the tufting operation.
In addition, Spanel Applications Ser. No. 474,264 and Ser. No. 474,265, filed concurrently with the subject application, disclose tufting systems in which the subject invention may be utilized.
In tufting developments which are related and take advantage of Spanel concepts, Ellison British Specification No. 1,339,594 discloses a clamp means which is utilized with Spanel double needles but which, however, is structurally and operationally sharply dissimilar. The Ellison clamp extends through the upper portion of each set of needles as contrasted to the subject clamping means which is described herein.